1. Field of the Invention
The present invention relates to a method of treating a surface of an aluminum or aluminum alloy (hereinafter referred to as an aluminum article), and more particularly to a method of forming grain-like or wooden like patterns on the surface of the aluminum article.
2. Description of the Prior Art
Heretofore, various patterns such as grain-like pattern and so on have been formed on the surface of the aluminum article by any one of the following methods:
(A) a method of embossing given pitches on the surface of the aluminum article with a transfer roller or a press molding tool;
(B) a method of etching the surface of the aluminum material into a pattern corresponding to an original with chemicals by a photoengraving process;
(C) a method of partially masking the surface of the aluminum material with an appropriate protective material so as to conduct spraying and baking of a paint or a chemical dyeing treatment or a method of coloring an oxide film formed on the aluminum article; and
(D) a method of printing the surface of the aluminum material with a paint or other coloring agent by screen printing or transfer printing.
And also, there is known a method of sticking a grain-like printed paper or film on the surface of the aluminum article. Among them, however, the method (A) is to strongly compress the aluminum article between a pair of dies or molding tools under pressure, so that it is only applicable to flat aluminum articles and also the manufacture of dies or molding tools requires much cost. Furthermore, in the methods (B), (C) and (D), the masking work and the printing of grain-like pattern not only require a great amount of labor, but also the subsequent secondary treatment is very troublesome and further there is a problem in the durability of layers patterned on the aluminum article. In any case, it is necessary to use specific machines and instruments, so that the working cost is very expensive, and particularly the above mentioned methods can not be applied to aluminum articles having complicated forms such as extruded profiles for aluminum sash and the like.